Field of the Invention
The present invention relates to a liquid discharge apparatus configured to discharge liquid.
Description of the Related Art
Liquid discharge apparatuses discharging liquid from nozzles have discharge failure in some cases. The causes of the discharge failure include, for example, the increase in viscosity of liquid in the nozzle which results from dryness (hereinafter referred to as “thickening of liquid”) and mixing of bubbles in a liquid channel. The discharge failure causes such a situation that the liquid is not normally discharged from the nozzle. There have been conventionally known various technologies for inspecting discharge failure of the nozzle, such as the technology for inspecting discharge failure without discharge of liquid from the nozzle.
The typical liquid discharge apparatuses include a printing head of an ink-jet recording apparatus. For example, there is known a printing head including: a nozzle plate in which nozzles are formed; a waveguide formed in the nozzle plate to extend in a nozzle row direction; a light source introducing light into the waveguide; and a light receiving part detecting an amount of light travelling through the waveguide. In the case of inspecting the discharge failure of the nozzle, pressure change is given to liquid in the nozzle to an extent that no liquid is discharged. Specifically, pressure change is given to the liquid in a state that light is introduced from the light source along the waveguide, thereby vibrating the meniscus of liquid in the nozzle.
The vibration of meniscus in the nozzle having no discharge failure is different from the vibration of meniscus in the nozzle having discharge failure. When the meniscus in the nozzle having no discharge failure vibrates, the meniscus is greatly drawn into the nozzle. Thus, the light introduced into the waveguide travels therethrough with little leakage from the nozzle and is received by the light receiving part. On the other hand, when the meniscus in the nozzle having discharge failure vibrates, the meniscus is hardly drawn into the nozzle. Thus, a part of the light introduced into the waveguide leaks in the nozzle, thereby reducing an amount of light received by the light receiving part. Namely, whether or not the nozzle has discharge failure can be determined on the basis of the amount of light received by the light receiving part.
Further, the typical liquid discharge apparatuses perform a predetermined recovery operation for the nozzle having discharge failure. The recovery operation is performed to recover the discharge performance of the nozzle having the discharge failure. The recovery operation may be meniscus vibration, preliminary discharge (flushing), suction cleaning (suction purge), and the like.